drm/nouveau: add support for MSI

Only supported on NV50+ so far, and disabled by default currently.  The
module parameter "msi=1" will enable it.

There's a kernel bug which will cause this to fail if the module (or the
NVIDIA binary driver) has ever been loaded before loading nouveau with
MSI enabled.  As such, this is only safe to enable if you have nouveau
load on boot, and don't wish to ever reload it.

The workaround is to "echo 0 > /sys/bus/pci/devices/<device>/enable"
until the enable count reads 0.  Then you should be able to load nouveau
with MSI enabled.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_drv.c

@@ -115,6 +115,10 @@ MODULE_PARM_DESC(perflvl_wr, "Allow perflvl changes (warning: dangerous!)\n");
 int nouveau_perflvl_wr;
 module_param_named(perflvl_wr, nouveau_perflvl_wr, int, 0400);
 
+MODULE_PARM_DESC(msi, "Enable MSI (default: off)\n");
+int nouveau_msi;
+module_param_named(msi, nouveau_msi, int, 0400);
+
 int nouveau_fbpercrtc;
 #if 0
 module_param_named(fbpercrtc, nouveau_fbpercrtc, int, 0400);

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -593,6 +593,8 @@ struct drm_nouveau_private {
 
 	struct nouveau_bo *vga_ram;
 
+	/* interrupt handling */
+	bool msi_enabled;
 	struct workqueue_struct *wq;
 	struct work_struct irq_work;
 	struct work_struct hpd_work;
@@ -754,6 +756,7 @@ extern int nouveau_force_post;
 extern int nouveau_override_conntype;
 extern char *nouveau_perflvl;
 extern int nouveau_perflvl_wr;
+extern int nouveau_msi;
 
 extern int nouveau_pci_suspend(struct pci_dev *pdev, pm_message_t pm_state);
 extern int nouveau_pci_resume(struct pci_dev *pdev);
@@ -872,6 +875,8 @@ extern int nouveau_ioctl_gpuobj_free(struct drm_device *, void *data,
 				     struct drm_file *);
 
 /* nouveau_irq.c */
+extern int         nouveau_irq_init(struct drm_device *);
+extern void        nouveau_irq_fini(struct drm_device *);
 extern irqreturn_t nouveau_irq_handler(DRM_IRQ_ARGS);
 extern void        nouveau_irq_preinstall(struct drm_device *);
 extern int         nouveau_irq_postinstall(struct drm_device *);

drivers/gpu/drm/nouveau/nouveau_irq.c

@@ -68,8 +68,13 @@ nouveau_irq_preinstall(struct drm_device *dev)
 int
 nouveau_irq_postinstall(struct drm_device *dev)
 {
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+
 	/* Master enable */
 	nv_wr32(dev, NV03_PMC_INTR_EN_0, NV_PMC_INTR_EN_0_MASTER_ENABLE);
+	if (dev_priv->msi_enabled)
+		nv_wr08(dev, 0x00088068, 0xff);
+
 	return 0;
 }
 
@@ -1263,5 +1268,35 @@ nouveau_irq_handler(DRM_IRQ_ARGS)
 
 	spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
 
+	if (dev_priv->msi_enabled)
+		nv_wr08(dev, 0x00088068, 0xff);
+
 	return IRQ_HANDLED;
 }
+
+int
+nouveau_irq_init(struct drm_device *dev)
+{
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+	int ret;
+
+	if (nouveau_msi != 0 && dev_priv->card_type >= NV_50) {
+		ret = pci_enable_msi(dev->pdev);
+		if (ret == 0) {
+			NV_INFO(dev, "enabled MSI\n");
+			dev_priv->msi_enabled = true;
+		}
+	}
+
+	return drm_irq_install(dev);
+}
+
+void
+nouveau_irq_fini(struct drm_device *dev)
+{
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+
+	drm_irq_uninstall(dev);
+	if (dev_priv->msi_enabled)
+		pci_disable_msi(dev->pdev);
+}

drivers/gpu/drm/nouveau/nouveau_state.c

@@ -667,10 +667,7 @@ nouveau_card_init(struct drm_device *dev)
 	if (ret)
 		goto out_fifo;
 
-	/* this call irq_preinstall, register irq handler and
-	 * call irq_postinstall
-	 */
-	ret = drm_irq_install(dev);
+	ret = nouveau_irq_init(dev);
 	if (ret)
 		goto out_display;
 
@@ -701,7 +698,7 @@ nouveau_card_init(struct drm_device *dev)
 out_fence:
 	nouveau_fence_fini(dev);
 out_irq:
-	drm_irq_uninstall(dev);
+	nouveau_irq_fini(dev);
 out_display:
 	engine->display.destroy(dev);
 out_fifo:
@@ -772,7 +769,7 @@ static void nouveau_card_takedown(struct drm_device *dev)
 	nouveau_gpuobj_takedown(dev);
 	nouveau_mem_vram_fini(dev);
 
-	drm_irq_uninstall(dev);
+	nouveau_irq_fini(dev);
 
 	nouveau_pm_fini(dev);
 	nouveau_bios_takedown(dev);